Method of treating phosphate rock.



CHARITES N. MERIWETHER, F TRENTON, KENTUQKY.

METHOD OF rnnnrmernosrna'rn ROCK.

No Drawing.

' Specification of, Letters Patent. Application filed November 14, 1910.SeriaLNo. 592,239.

Patented Sept. 5, 1911.

To all whom it may concern:

Be it known that I, CHARLES N. MERI- WETHER, a citizen of the UnitedStates, re-

siding at Trenton, in the county of Todd and State of Kentucky, haveinvented certain new and useful Improvements in Methods of TreatingPhosphate Rock; and I do declare the following to be a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

This invention relates to a method of treating tribasic phosphate oflime to render the phosphoric acid therein soluble and available. v

The object of the invention is to change the natural or neutralcondition of natural mineral deposits to render the phosphoric acidcontained therein available for plant fertilization without the use ofsulfuric acid, which latter is commonly employed for this purpose but isexpensive and also injurious to the. plants.

The accepted test employed by agricul-' tural chemists to ascertain theavailability of the phosphoric acid is to subject a sample of theprepared fertilizer to a two per cent. citric acid solution, which willdissolve a large part of the phosphate in said sample if the fertilizeris in proper condition to be used for a plant food.

This invention resides in the discovery of the fact that freshly formedbasic oxid of iron, that is,-nascent basic oxid of iron, will absorbphosphoric acid from the tribasic compound and render it tetra'basic andsoluble in the two per cent. citric acid solution. This transformationwill take place slowly at ordinary temperatures but will be greatlyfacilitated by subjecting the compound to heat belowthe fusing point andagitating it while heated. It is important that the temperature be keptata point below fusing, as otherwise the silica which is usually foundin the rock will take the lime from the phosphoric acid and reduce itagain to an insoluble state, the resulting mass bleing in they formof avery hard vitreous s ag.

I have discovered a simple and etficient method of' producing the basicnascent oxid of iron in the presence of the tribasic calcium phosphateand at the same time avoid the silica acting on the lime. This methoddiffers somewhat acoordin'gto the nature of 'Metallic iron may the rockto be treated, for instance, if the rock contains fluorid it isparticularly apt to melt and vitrify with the lime and silica. 1

In treating phosphate rock containing 65 per cent. tribasic phosphate oflime and 35 per cent. silica, I add to one hundred pounds tractionfor-phosphoric acid which it absorbs from the lime changing it from atricalcic to a tetracalcic phosphate. It is important that the phosphaterock and iron ore be finely pulverized and intimately mixed, as there isno fusion chemical action can only take place between surfaces in actualcontact, and the finer the material is pulverized and more intimately itis mixed the more surfaces are in actual contact and the quicker will bethe chemical action and the less heat will be required to liberate thephosphoric acid. If. the temperature is raised too high for instance, toa bright yellow or white heat, a reaction setsin between the silica andthe lime of the tetracalcic phosphate injuring the solubility of theresulting fertilizer. Should the fusing point be reached the iron orewill be reduced to metallic iron and the phosphoric acid which it hastaken from the .tribasic phosphate of lime will be reduced tophosphorus,

and a part of it escapes as gas together with the gases of combustionand is lost, and part unites with the reduced iron and is thereby Inmany cases it has been found advantageous'to substitute metallic iron orpartially reduced ore for the natural ore, especially so whenthe'phosphatero'ck is found to contain a large per cent. of iron. The

turnings and filings from machine shops may be used to supply themetallic iron. e used alone and will alkalis rather than the phosphatebecome converted into a basic oxid at a no low red heat and when so.converted will accomplish the change in the phosphate rock to ren er thephos horic acid therein soluble.

The agitation ot the compound while being heated is advantageous in that1t brings new surfaces of the particles of iron OXld and phos hate rockinto contact thereby permittmg the chemical action andit also keeps Ithe material in a pulverized condition, thereby rendering it unnecessaryto regrin'd the resulting product.

Other metals may be used, instead of iron or in connection wlth it. Todo-this I produce the basic oxid of iron beforehand and grind it and thephosphate rock together with 'the other salts. The violent breakingapart and the bringing together of freshly broken surfaces contributesto chemical re-j action. Salts of barium, potassium sodium, ammonium;and magneslum may be used.

-Or the ferro-cyanid of potassium, which ing the rock and combining itwith pulverized basic oxid of iron.

- 2. A process of treating phosphate rock to render the phosphoric acidcontained therein available, wh1ch comprises pulverizing the rock andcombining it with pulverized basic oxid of iron and heating thecompoundto a temperature below fusing.

3. A process of treating phosphate rock to render the phosphoric acidcontained therein soluble,swhich comprises pulverizin the rock andcombining it with pulverize iron ore at atemperature below fusing point.

:1. method of rendering the pho horic ac d in phosphate rock available,whic comprises pulverizing the rockand mixing it with a mixture ofpulverized iron ore and iron and then heating the compound to. atemperaturebelow fusin V 5; A method of renderm the phosphoric acid inphosphate rock avai able, which comprises pulverizing the rock. andmixing it with a mixture of pulverized iron ore and iron and thenheating the compound to a temperature below fusing and thoroughlyagitating said compound during the heat mg process. 4

6. A method of rendering phosphoric acid in phosphate rock available,which consists in mixing phosphate rock with oxid of iron and iron and asalt of potassium and grindin them so as to break up the particles andbring fresh surfaces togetherthereby producin a transfer of art of thephosphoric acid rom the phosphate rock to the other bases withoutfusing.

In testimony whereof I have hereunto set my hand in presence of twosubscribing wit- OHARLES N. MERIWETHER. Witnesses:

E. H. Droxmson,

E. R. THOMPSON.

